Upper supports are used in medium-weight and heavy turning machines. They serve to mount the turning tools and to absorb the forces transferred from tools, through the upper support and into the machine bed. An upper support always rests on a bottom slide which, in turn, is drivable on a bed carriage in a direction transverse to the machine bed. In order to execute several types of turning with the same upper support, the upper support can be turned with respect to the bottom slide in steps of 90.degree..
The known rotatable upper supports, however, have the disadvantage that they have no fixed stops for the turning tool. Thus, for example, the upper supports in their normal position are capable of tooling the left shoulder of a workpiece from the right. Now, if it is desired to tool a corresponding right shoulder from the left, then for this purpose the upper support has to be rotated through 180.degree. and thereupon the turning tool carrier with the turning tools mounted thereto has to be changed over. The upper supports in which this is possible have a clamping device for receiving the generally bar-form turning tool carrier, which can be formed, for example, by two parallel plates, which are joined with one another by force clamps. Another possibility for fastening the turning tool carrier includes the use of a horizontal groove arranged laterally in the upper support, in which groove the turning tool carrier is guided and clamped fast. In none of the known rotatable upper supports, however, is there provided a means of securing the turning tool carrier so that the cutting edge of the turning tool can be held at a firmly prescribed and exactly measured point. For this reason in the known upper supports it is always necessary, after a tool change, to remeasure the position of the cutting edge and to readjust it. This means, of course, an undesired expenditure of labor.
On the other hand, neither is it possible to dispense with the use of rotatable upper supports, since when the upper support is arranged for the tooling of a left shoulder, it stands in its own way in the tooling of a right shoulder unless it is turned through 180.degree..
Underlying the present invention, therefore, is the problem of providing a rotatable upper support whose handling is facilitated and which can be used much more versatilely than was hitherto the case.